Topside sounder Ne profiles The goal of the project was to produce Alouette-2, ISIS-1 and ISIS-2 digital topside ionograms from selected original 7- track analog telemetry tapes. More than ½ million digital topside ionograms are now available for downloading at ftp://nssdcftp.gsfc.nasa.gov.ftp://nssdcftp.gsfc.nasa.gov TOPside Ionogram Scaler with True-height (TOPIST) algorithm was developedto automatically scale digital ionograms
Дефиницията на scale height и transition height – ключ към използуването на огромната база данни на topside sounders O+ scale height = dh/d(lnNe)
Definition of O + scale height H T and transition height h T The database, archived at the National Space Science Data Center (NSSDC), Greenbelt, MA, includes 176,622 topside electron density (Ne) profiles from the Alouette-1a, -1b, -1c and -2 and ISIS-1 and -2 topside sounders, covering the period 1962-1979. A detailed description of the database is given by Bilitza (2001).
Database –O + scale height H T Imposed limits : (200-1500) km for h T, (0-600) km for H T. The database contained only pairs of h T and H T data. This reduced the total number of measured profiles with 3.7%. The histograms of percentage distribution of H T values (left panel) and its longitude coverage. The most likely H T value is around 100 km, as 90% of them lie within the range (50-200) km. The longitude distribution is highly non-uniform. One-half of the data have longitudes between 250º and 310º.
Database –transition height h T The O + scale height obtained by the regression contains the 30% increase of plasma temperatures. Simple theoretical considerations assure that the transition height should not change considerably when plasma temperature varies, although the density changes. The increased plasma temperature increases also the H + scale height with the same proportion as that of O + (with opposite sign). Therefore, near the transition height both ion densities increase, but the altitude where they become equal does not change.
H T / h T ratio It was found that the scale height and transition O + -H + height, extracted from each individual measured Ne profile, highly correlate, with a correlation coefficient exceeding 0.8 at midlatitudes. The upper panel shows the model prediction, while the lower panel shows individual values in a H T /h T plot, taken from (30, 50) geomagnetic latitude in daytime winter. The ratio H T /h T obtained from the individual profiles is modelled as a function of same input parameters as H T and h T.
The new Topside Sounder Model (TSM) The scale height H T, transition height h T and their ratio Rt are modeled separately by the same type of polynomial. month: c 0 + c 1 sin(x) + c 2 cos(x) + c 3 sin(2x) + c 4 cos(2x) local time: c 0 + c 1 sin(x) + c 2 cos(x) + c 3 sin(2x) + c 4 cos(2x) glat: c 0 + c 1 x + c 2 x 2 + c 3 x 3 + c 4 x 4 + c 5 x 5 + c 6 x 6 sf: c 0 + c 1 x + c 2 x 2 Kp: c 0 + c 1 x + c 2 x 2 The new Topside Sounder Model (TSM) provides H T, h T and Rt for any set of above shown parameters in their defined ranges.
Model results – daytime Individual daytime (10- 16 LT) values of h T, H T, and their ratio Rt (red crosses) from winter (left) and summer (right) months. Solar flux (F 107 ) ranges between 80 and 120, Kp>4. Model values (blue curves) refer to LT = 12 on January 1 st (left) and July 1st (right), SF=100 and Kp=3.
Model results - nighttime Individual nighttime (22-04 LT) values of h T, H T, and their ratio Rt (red crosses) from winter (left) and summer (right) months. Solar flux (F 107 ) ranges between 80 and 120, Kp>4. Model values (blue curves) refer to LT = 00 on 1 st January (left) and 1 st July (right), SF=100 and Kp=3.
Model results – local time dependence Individual values of h T, H T, and their ratio Rt (red crosses) from winter (left) and summer (right) months versus local time. Solar flux (F 107 ) is limited to (80, 120), Kp<4. Model values (blue curves) refer to geomagnetic latitude 40 N for January 1 st (left) and July 1st (right), SF-100 and Kp=3.
TSM performance TSM provides h T, H T, and Rt as functions of month of the year, local time, geomagnetic latitude, solar flux (F10.7), and Kp index TSM parameters averagedispersion around average relative dispersion model error relative model error hThT 862 km334 km40 % 268 km 28 % HTHT 138 km54 km39 % 36 km 26 % Rt= H T /h T 0.170.0425 % .003 18 %
Latitude (HSA) SCALE HEIGHT NeQuick: (unusually) high values in the north hemisphere PIM: highest values in summer, (unusually) high during the day NeQuick: large differences between the hemispheres ( + discontinuity )
Latitude (HSA) TRANSITION HEIGHT NeQuick: sharp discontinuity over the equator observed in the latitude profile of the transition height
TSM Profiler (TSMP) = F2(h) TSMP дава формата на профила. Самият профил се получава като се спесифицират NmF2 и hmF2
Съвременните йоносонди Digisonde на Lowell University (Bodo Reinisch et al) автоматично изчисляват електронния профил Ne под hmF2 и в добавък дават една оценъчна scale height Hm (в предположение на α- Chapman разпределение около и над hmF2). Тази величина Hm впоследствие се използува за реконструкция на Ne в над- максимумната (topside) част на областта F. Hm във формулата на α-Chapman представлява scale height на неутралната атмосфера. На височини достатъчно над hmF2, α- Chapman профила намалява експоненциално с градиент съответствуващ на 2 Hm. Наличието на Hm, екстрактирана от реално измерени йонограми, дава възможност за комбиниране на измерванията на Digisonde с моделните параметри на TSMP. Ако моделната H T се замести с Hm, то Digisonde посредством моделното отношение Rt може да получи подходящо преходно ниво h T и оттам да възстанови целия профил.
Scale height: TSM (H T ) vs Digisonde (Hd) One year of data from Athens, Juliusruh, Chilton and Millstone Hill (Oct. 2000-Sep 2001) are used for the analysis. Digisonde derived Hm is multiplied by 2 to represent the plasma scale height, denoted as Hd (Hd=2*Hm). TSM provides ht, H T, and Rt for each Digisonde measurement. So, we have for any measurements a set of foF2, hmF2, Hd, h T, H T, and Rt. The histograms of all Hd and H T values show that Hd is systematically lower than Hs. TSM H T Digisonde Hd
Scale height Histograms Digisonde Hd distribution is compared with the H T extracted from all available topside sounder Ne profiles. Red: Digisonde Scale Height Hd Green: TSM Scale Height Hs
TSMP & Digisonde profiles Red curves show Digisonde – Chapman profiles. Dashed red curve shows O + with Hm from ionogram. Solid red curve shows O + profile with Hm multiplied by a factor of 2.4 (=2*1.2). H + density is obtained by TSMP for H Т =1.2Hm The total density Ne of TSMP (using H Т ) and Digisonde &TSMP agree very well NmF2 = 6.6 E5 hmF2 = 406.7 km Hm = 41.4 km H T = 99.36 km h T = 880.6 km DIG O+ (Hm*2.4)